Traumatic injury remains the number one cause of death for Americans between 1 and 44 years of age. The economic consequences of trauma related injuries are estimated at over 44 billion dollars in direct costs and over 400 billion dollars per year in productive life years. While most patients survive after arrival to the hospital, rapid and effective methods for improving hemodynamics after traumatic injury are urgently needed to reduce mortality rates from traumatic injury. This Phase 1 application is focused on a novel non-invasive device called the intrathoracic pressure regulator (ITPR), designed to enhance circulation in non-breathing hypotensive patients. The ITPR is designed to "buy time" before fluid resuscitation or more definitive care is available. Building upon the development of the inspiratory impedance threshold device (ITD), designed and demonstrated by the applicants to increase survival rates in patients in cardiac arrest and to increase blood pressure in hypotensive patients who are able to breathe spontaneously, the ITPR is a non-invasive intrathoracic pressure device that rapidly increases circulation and blood pressure in severely hypotensive patients. The ITPR attaches to the patient's airway, generates a small but continuous negative intrathoracic vacuum and thereby immediately increases blood pressure by drawing more venous blood back into the heart when not providing intermittent positive pressure ventilation. Simultaneously this device lowers intracranial pressure. Preliminary animal studies with the ITPR demonstrate that mean arterial pressures as well as coronary and cerebral perfusion pressures are rapidly increased with application of the ITPR. This Phase 1 investigation proposes to a) improve the safety and efficacy of the ITPR by a) determining the optimal vacuum needed to improve circulation, b) making and evaluating bioengineering design changes in the current prototype and c) demonstrating proof of concept by assessing neurologically intact survival rates and pulmonary complication rates with and without the ITPR in a porcine model of hemorrhagic shock. If successful, Phase 2 studies will address the potential clinical efficacy of the ITPR in patients in hemorrhagic shock. Use of the ITPR is expected to significantly increase patient resuscitation rates, based upon the improvement in blood flow to the heart and brain observed in animal studies. If a significant clinical benefit is demonstrated, the ITPR would become a standard piece of resuscitation equipment for hypotensive patients with traumatic injury and other causes of hypovolemic hypotension.